Composition of matter, coated article, and methods of making the same



. metals in sheet form.

Patented Feb; 12, 1946 UNITED TA PATENT mmor mama. COATED ARTI- AND oomosrrron V No Drawing.

Application May 1'7, 1943, Serial No. 487,348

Claims. (01. 117-75) This invention pertains to a new composition of matter and to the coating ofsurfaces such as The invention pertains more particularly to the coating of sheet metal which is to be fabricated into objects by stamping, bending, creasing, drawing, threading, turning, punching, and the like.

Because of the great economical advantage of coating the sheet metal prior to the various forming operations, the importance of a film or film system which will withstand the various forming operations without injury cannot be overestimated.

Another quality of extreme importance, particularly in the case of certain uses to which the. finished articles are to be put. is the relative insolubility and chemical inertness of the film or film system.

An outstanding example of such a use is in the food packaging field in which metal cans and metal foil wrappings are extensively used.

The term food is employed herein to mean that which is eaten or drunk or absorbed for nourishment or otherwise, and include not only beverages such as beer, but also substances from which food is prepared, examples of which are coffee beans, whether ground or not, and tea leaves.

In the case of cans. for example, economical considerations make it extremely advantageous to apply the film or film system to the sheet metal while in the fiat. Th can parts are then cut, shaped and joined all in a manner well known in the art. Severe stresses are set up during the formingoperations, particularly in the case of the die-drawing of the can ends. The can ends and portions of the can body are again subjected to severe stresses by the seaming chuck, seaming rolls, and cooperating parts of the can closing machine during the well known double-seaming can sealing operation.

Metal caps are used in large quantity not only on glass bottles but also on certain types of metal containers, such as those for holding beverages.

In many cases, such caps are provided with threads for engaging cooperating threads upon the bottle or other container.

The operation for forming metal caps is extremely severe.

In the case of metal foil wrappings, as is well known the foil is usually drastically and sharply creased informing the food packages, as well as by the user in opening and closing the packages.

the threads in the i The coating on the foil therefore must be capable of successfully withstanding very'severe stresses.

In the food. packaging field it is, of course, absolutely essential that the film -or film system be not only completely insoluble and chemically inert, but also completely-incapable of impartin taste or odor to the food product.

In addition to the foregoing, there are certain metals which are extremely difilcult to coat with satisfactorily adhering films or film systems of any character. Examples'are zinc, zinc plate, magnesium and magnesium alloys, such as the material known commercially as Dow metal."

In accordance with my invention, single film systems and multiple film systems having the above desirable properties may be produced by forming (a) said single film system, or (b) the primer coat or a multiple film system provided the top coat is of a satisfactory character, or (c) the top coat of a multiple film system provided the primer coat is of a satisfactory character, with a liquid coating composition having .as a base resinous benzene-soluble hydrogenated ized cyclopentadiene employed in my new composition of matter has the following'properties. It is soluble in benzene, toluene, chloroform, carbon tetrachloride and high flash naphtha, and insoluble in water. Forthe purpose of conven ience in the claims, these solubility characteristics will be defined by the term fbenzene-soluble, though it is to be understood that the actual presence of benzene in the liquid coating composition or in the applied films is not imp1ied,,nor is it implied that the hydrogenation is in the presence of benzene. Preferably, my composition containing a substance of the type described has other distinctive properties. Among these properties is the ability to form a smooth, glossy, highly flexible and extensible and tenaciously adhering film upon dryingwith or without baking.

The preparation, of benzene-soluble hydrogenated benzene-soluble catalytically polymerized cyclopentadiene employed in my invention is described and claimed in my copending application, Serial Number 262,655, filed March 18,

1939, which will mature into Patent 2,319,271,

' Camphor method.

' when hydrogenation drogenation 'whic drogenati on mEy be either partial or complete,

such as substantially complete.

Hydr genated polymers of "character, generally"speaking, have an average of molecular weights above 350, and especially above 400, for example, above 450; as determined by the Rest ably determined by the Staudinger viscosity method, (Ind. and Engr. Chem., vol. 32, page 299, 1940) which is better adapted to the determination of high molecular' weights than the Rest method. The Fast Camphor method, however, is suitable for determining whether the molecular weight is higher than any of the lower limits given.

In accordance with my'present invention a sulfur-containing material (which term for brevity is to be construed as including sulfur) in suitable I quantity is added to benzene-soluble hydrogenated resinous polymerized cyclopentadiene prior to the final drying (as by baking) of such hydroe genated polycyclopentadiene upon the surface to be protected. I

. Usually, the addition of the sulfur-containing material is made prior to the application ofthe benzene-soluble hydrogenated catalytically polymerized cyclopentadiene to the surface or object to be coated. Thus a sulfur-containing material.

' such as flowers of sulfur, may be added to said hydrogenated polycyclopentadiene prior to its application to the surface to be coated.

However, theaddi'tion of a sulfur-containing material to the hydrogenated polycyclopentadiene may be made after the latter has been applied to the object to be coated, for instance, by baking said object in an atmosphere comprising hydrogen sulfide or other sulfur-containing ma-' terial in which case the sulfur-containing material is absorbed by the hydrogenated polycyclopentadiene from the atmosphere particularly Gigi partial.

Thus, the coated position comprising benzene-soluble hydrogenated catalytically polymerized cyclopentadiepe in admixture with a sulfur-containing material and the coatings of benzene-soluble hydrogenated catalytically polymerized cyclopentadiene may therefore be said to be dried in admixture with a sulfur-containing material.

Both methods may be combined, if desired,' that is the object or surface to be protected may be coated with benzene soluble hydrogenated catalytically polymerized cyclopentadiene which already contains a sulfur-containing material, such as sulfur or hydrogen sulfide, and then the coating may be dried such as by baking in an atmosph like.

By thus incorporating ;a sulfur-containing materia withbenzene-soluble hydrogenated catalytica ly polymerized cyclopentadiene, the'properties of the finished resin film are desirably modified. 3 4

The addition of a sulfur-containi'ng material such as sulfur will also tend to reduce the rate of oxidation of the hydrogenated polycyclopentadiene film particularly in the case of partial hyh may be desirable in some inere comprising hydrogen sulfide or the stances. a

It will be understood that the optimum ratio of additives to be employed may vary somewhat, depending upon factors such. as'the particular ad- 7 ditive, the manner of drying employed, etc. While Actual average molecular 1 weights if much higher than 450, may be preferects may be said to be coated with a dried film of a liquid coating comsulfur as additivemay be employed in concentrations of as low as 0.1% (based upon the hy- V drogenated polycyclopentadiene present in the "coating solution) with improved results, general- 1y speaking concentrationsin excess of 8% and particularly those lying in the range of from 10 tozl6-%, ,willgive very satisfactory results. The maximum quantity employed preferably depends upon the "solubility of the additive in the polymer solution, which in turn depends upon the hydrogenated polycyclopentadiene concentration although it is conceivable that some of the additive may be present in a finely divided dispersion.

Higher concentrations of additives may be obtained by supersaturating or by dispersing. The ratio of additive employed may be varied considerably, depending upon factors such as the particular nature of the additive, the manner .of dryin etc.

An example of the formation of a single film system is as'follows:

Example 1 coats with or without intermediate 'drying such as by baking, will have a desired thickness, for. example the equivalent of from 4 to 6 milligrams per square inch of dry film.

Place the coated sheet in an oven and heat to a temperature, for example, of 250 F. for a period of about 15 minutes in order to insure satisfactory drying. Alternatively, drying may take place 40 at room temperature such as between 1 hour and 6 hours or more as required.

Sheet metal thus coated is capable of withstanding drastic forming operations such as encountered in the manufacture of cans or other containers, container caps and the like.

An example of the formation of a .dual film system is as follows:

- Example 2 Coat a tin plated sheet, or other metal sheet, with a solution of hydrogenated resinous polycyclopentadiene intoluene, say of 20% hydrogenated polycyclopentadiene content, to which 5% sulfur based on polymer content has been added. Apply the solution in sufiicient quantity to secure a desired final coating weight, say of approximately 1 /2 milligrams per square inch after drying,such.as by baking.

Place the coated sheet after suitable evapora- 50 tion of solvent in an oven and bake at a temperature of say- 2 50". F. fora minutes. I

Upon cooling, app y a solution of Vinylite in sufficient quantity such that the dual film system Q! will have adesired thickness after drying of the "Vinylite film such as with baking, say. a thickness equivalent to 4 to 6 milligrams per square inch of dry dual film.

- N Then rebake the coated sheet in the same man- 1| It will be' understood, of course, that broadly period of 5 to 1o speaking, the top coat is not limited to Vinylite, which is the coplymer of vinyl acetate and vinyl chloride, but may be a polymer or any of the vinyl compounds used as raw material for the several vinyl resins; for example, vinyl acetate, vinyl chloride or vinyl chloracetate. In fact, other types of resins may be adapted for application as the top coat over my benzene-soluble hydrogenated benzene-soluble .catalytically poly-' merized cyclopentadiene containing additives as described. Vinylite is thought to result from polymerization of about 85% of vinyl chloride with about vinyl acetate, although other proportions are possible.

Since my films of hydrogenated polycyclopentadiene plus additive not only bond well to surfaces but also are highly resistant to-attack by foods, and do not'impart taste or odorthereto, they may be used as top coats for primer coats of other materials, if desired. It is, of course,

understood that my liquid coating composition may be used for both a primer coat and atop coat or in any other number of coats.

It will be understood that other sulfur-containing substances might be employed as addithe cotrary, I may heat or'bake-the coating or the coated object in an atmosphere substantially devoid of oxygen such as an atmosphere of concentrated Has and/or in an inert gas as of nitrogen, carbon dioxide, or the like. i

: Additional drying or hardening of the film ma result from the absorption of oxygen after exposure to the atmosphere depending upon the degree to which the polycyclopentadiene has been hydrogenated.

,Thus the drying or hardening of a film of hydrogenated polycyclopentadiene containing sulfur-containing material may be secured (a) by baking or' heating in an oxygen-containing and/or sulfur-containing atmosphere, or (b) baking in an atmosphere devoid of oxygen followed by exposure to an oxygen-containing atmosphere for a period of time, for example a week before applying any top coating, if applied, such as of Vinylite, or (0) baking in an atmosphere devoid of oxygen, followed by application of'a top coat, if used, and then letting the dual film stand or season in contact with an oxygen-containing tives instead of, or together with, those already Thus, for example, 12% hydrogen going, or otherwise.

3% butyl zimate: either alone or with varying amounts such as from 1% and 3% sulfur, are among the additive combinations that may be employed with hydrogenated polycyclopentadi'ene to give resin films on sheet metal capable of withstanding drastic; shaping and forming operations.

With respect to'th'e temperature and time of baking, I usually'prefer to rarely if ever exceed about 400 F. and at such temperatures a baking time not longer than about 15 minutes to avoid any possible injury to the film. However, while my resin films may be safely subjected to relatively high temperatures for brief periods durin baking, in general, temperatures up to 350 F. with baking times up to 30 minutes will be satisfactory. With higher temperatures the baking time may be correspondingly shortened to yield similarly satisfactory results.

A particularly satisfactory baking scheduleis represented by a-temperature of 250 F. for a period such as'from 10 to 15 minutes. Another satisfactory baking schedule is represented by a procedure wherein the temperatureduring the bake is gradually raised from about room temperature to the maximum desired temperature such as about 250 F. over a period such as from 15 to 20 minutes. The advantageof a bakin schedule such as the latter is that th'esolvent is driven off more gradually, thus minimizing or eliminating any tendency for the resin film to be ruptured by escaping solvent.

While I refer herein to "baking broadly and to heating in the presenceof air or anfoxygen-containing gas as a means of drying my coating or film, it is to be understood that-the taking on of oxygen by the film, if this takes place at all, need not necessarily take place simultaneously with the heating'or baking. On' the conatmosphere before using the coated article for its intended purpose (in the last-named case, oxygen ma penetrate or seep through .the top coat to the primer coat), or (d) applying and drying the primer coat in an atmosphere .devoid of oxygen, coating with a top coat of another resin such as Vinylite, still in an atmosphere devoid of oxygen, or (c) any combination of any of the foreent'sulfur-containing material, if desired.

M modified hydrogenated resinous polycyclo pentadiene films may be satisfactorily hardened either by heat, or by an oxygen-containing and/or sulfur containing environment or by any combination thereof, or otherwise.

In fact, other drying or hardening methods might be employed.

While the film thicknesses given are suitable for the purpose, and particularly for metal container elements such as foodcontainers and caps, other film thicknesses may obviously be employed without departing from the spirit of the invention.

While in the used, 'it is to be understood that other suitable solvents may be employed of which benzene, xylene, ethyl benzene, na'phtha, chlorofo;rm and carbon tetrachloride, are examples.

While the foregoing particular description has been concerned primarily with the 'application- =of the protective film or films to metal sheets of a gauge used in the manufacture of articles such as caps and tin cans, it will be obvious that my invention is not limited thereto but may be applied'to any metal sheet material, and in fact, to metallic objects in general whether pre-fabri cated or not,. where a tough strongly adhering film or fihn system is desired. The fabrication of toys from sheet metalfor instance, represents,

another importantfield of applicationfor my invention.

Thus, the resin film may be applied to metal foil.

As an illustration, tinfoil and aluminum foil, each of which is used to package dairy products like butter :and cheese, maybe so coated. If de-'- sired, these materials in molten form maybe poured into molds lined with foil coated in accordance withmy invention.

So too, lead foil, such as is used to package tea It will be understood that an atmosphere devoid of oxygen may have presabove specific examples toluene is cedure. For example, 'the foil may be passed through a solution of the coating material and the excess removed by means of doctor blades orrolls. Or a, conventional roll typ coating procedure maybe employed and the solvent re- .moved and/or recovered in any suitable manner.

Or the coating material may be poured or sprayed on the material to be coated and the excess re-.

moved by doctor blades or rolls, or simply allowed to drain away.

If desired, metal foil may be strengthened by baking it with paper, or by laminating two or more foil layers. For example, a sheet of metal foil ma be coated on 'one side and: the coated side pressed intocontact witha sheet of paper or second sheet of foil before the coating material has completely dried. This may be followed by coating the opposite side of the metal foil and drying the film for contact with foodstufis. On the other hand, metal foil coated with my dual film system with Vinylite" as the top coat may be hot pressed against paper or foil to eilect union of the materials. i

' While the invention has. been more particularly described in connection with the-coating of sheet metal including foil in the fiat, my resin film or film system may be applied during or after any forming operations for converting the inierally useful for coating objects in general,

" ,whether fabricated fromsheet metal or not, or

benzene-soluble hydrogenated polycyclopentadiene is made, which is then modifiedby additives in the manner described, the presence or addition of relatively small-amounts of still other substances of a resin-forming nature with conse-' quent modified results may be sometimes desirable, providing the outstanding characteristics of the base material" are not substantially destroyed. Though in many instances I prefer to use the homopolymer of cyclopentadiene without other polymer as the material to be hydrogenated, homopolymer of methyl cyclopentadiene or copolymer of cyclopentadiene and methyl cyclopentadiene, or both, in amounts up to of the order of from to 20% and possibly more may be present during hydrogenation particularly for certain uses. This does not apply to resinous materials in general and extreme care should be exercised in making any additionsprior to hydroenation. V

I Up to 20% or more df'methyl cyclopentadiene may be present in-the starting material from which the polycyclopentadiene resin which is to be hydrogenated is prepared, particularly for certain uses, though its presence may be limited or excluded altogether. The absence of all other materials polymerizable under the .conditions employed is preferred.

After hydrogenation a suitable additional additive or additives, other than that to whi'chthis invention particularly relates may be also employedin regulated amount of which wax-like materials suchias wax-like fatty acid esters havcoated in accordance with my inextracted from petroleum 'oils; and inhibitors such as secondary aryl amines; are examples. Reference is made to my copendingapplications,

Serial NOS. 487,352; 487,350; 487,349; and 487,351,

all filed May 17, '1943, respectively.

While the invention has been described in considerable detail with respect to the use of hydrogenated catalytically polymerized cyclopentadiene containing an additive of the character particularly described, with or without the use of other additives, as a coating composition, it is to be understood that such compositions also may be used for other purposes for'which the peculiar properties of hydrogenated polycyclopentadiene make the compositionparticularly applicable, such as for the preparation of plastic masses in general.

If desired, suitable coloring materials may be i added such as dyes, pigments, and lakes. The

same applies with respect to the Vinylite top coat. However, in the food packaging field, care should be exercised with respect to any such added substances so as not to lower or destroy the excellent qualities of the original material for this particular use.

Since in the food packaging field the important consideration is that the resin in contact tial'material into the finished object. It is gening between 18 and 57 carbon atoms, for instance,

with the foodbe chemically inert, insoluble'in the foodstuff, 'incapa'bleof imparting odor and taste thereto, and-strongly adherent to the enclosing wall, outside portions of the container or foil may be left uncoated, or may be coated with other materials, particularly it suitable, or with my materials with or without modifying agents besides those already mentioned, or otherwise.

The starting materials employed in this invention namely benzene soluble catalytically polymerized cyclopentadiene, benzene-soluble catalytically polymerized methyl cyclopentadiene, and benzene-soluble catalytic copolymer of cyclopentadiene and methyl cyclopentadiene may be obtained from any desired source, for example,

by any of the processes described and claimed in U. S. Patents-2,314,902; 2,314,903; 2,314,904; 2,314,909; 2,314,910; and 2,314,911; 'all dated March 20, 1943; or in my copending applications Serial No. 414,278, filed October 9, 1941; Serial No. 415,220, filed October 16, 1941; and Serial No.

415,648, filed October 18, 1941.

These polymers, generally speaking, have molecular weights above 350, and especially. above 400, for example, above 450, similarly to ,the hydrogenated polymers.-

The hydrogenation of all these starting materials may-be carried out in all respects similarly to the hydrogenation of benzene-soluble catalytically polymerized cyclopentadiene or in other words benzene-soluble resinous polycyclopentadiene as describedand claimed my above mentioned copending application Serial No. 262,655,

filed March 18, 1939.

.The hydrogenation of benzene-soluble catalytically polymerized methyl cyclopentadiene and of catalytic copolymer of cyclopentadiene and methyl cyclopentadiene is described and claimed in my copending application Serial No. 487,356,

filed May 17, 1943.

For certain purposes, the surface active agent polymers such as the clay polymers of Serial No. 414,278 or the organic acid sulfate polymers such as the alkyl sulfuric acid polymers of Serial No. 415,220 are preferred for hydrogenation purposes.

For example, a, higher degree of hydrogenation particularly to activated clay polymers.

It will be noted that the starting materials are polymers of monomers as distinguished from polymers of dimers.

It will be understood that monomethlyl cyclomay be attained with a, given efiort. This applies 7 lar weight above 400 admixed with a sulfur conpentadiene may have three isomeric forms. Oi

group is attached to the carbon atom having only single bonds is generally speaking preferred.

While the invention has been described more particularly with respect to hydrogenated polyutilized for purposes other than that .of coating- .these three forms, the form in which the methyl of metals, which are to be drawn or deformed after coating and since they have utility in this field even though methyl cyclopentadiene or polymers of methyl cyclopentadiene are not restricted as suggested, it is to be understood that my new compositions of matter and their uses include the addition of my additive more particularly described to anyone or to any mixture of hydrogenated polymer of cyclopentadiene, hydrogenated polymer of methyl cyclopentadiene and/ or hydrogenated polymer of cyclo'pentadiene-methyl cyclopentadiene' mixtures without limitation as to the quantity of methyl cyclope'ntadiene present in such mixtures, or otherwise.

In the specification and claims, the term sulfur-containing is intended to embrace elemental sulfur as well as compounds containingone or more sulfur atoms in the molecule.

It is to be understood that the above specific examples are by way of illustration. Therefore, changes, omissions, additions,

drogenation of at least one of a group consisting of resinous polymerized cyclopentadiene, resinous polymerized methyl cyclopentadiene, and resinous copolymer of cyclopentadiene and methylcyclopentadiene in admixture with a sulfur containing rubber vulcanizing agent.

2. A new composition of matter comprising a.

benzene-soluble product having an 1 average molecular weight above 350 and resulting from the hydrogenation of at least one of-a group con-- sisting of resinous polymerized cyclopentadiene,

resinous polymerized methyl cyclopentadiene and resinous copolymer of cyclopentadiene and methyl cyclopentadiene admixed with a sulfur containing rubber vulcanizing agent.

3. A new composition of matter comprising benzene-soluble hydrogenatedresinous polymerized cyclopent a-diene having an average molecusubstitutions, and/or modifications may be made within the scope of the claims without departing from the taining rubber vulcanizing agent.

s 4. A new composition of matter comprising benacne-soluble hydrogenated resinou polymerized cyclopentadiene having an average molecular weight above 450 admixed with a sulfur contain ing rubber vulcanizing agent.

5. A new composition of matter comprising benzene-soluble hydrogenated resinous polymerized cyclopentadiene having an average molecular weight above 350 admixed with elemental sulfur.

6. A new composition of matter comprising benzene-soluble hydrogenated resinous polymerized cyclopenta diene having an average molecular weight above 350 admixed with hydrogen sulfide.

'I.-A coated article having applied thereto a dried film of a benzene-soluble product having an average molecular weight above 350 and resulting from the hydrogenation of at least one of a group consisting of resinous polymerized cyc1opentadiene, resinous polymerized methyl cyclopentadiene and resinous copolymer of cyclopentadiene and methyl cyclopentadiene in admixture with a sulfur containing rubber vulcanizing agent. 8. A containerfor food products comprising a metallic receptacle having on an interior surface thereof a dried film of hydrogenated resinous polymer of cyclopentadiene in admixture with a sulfur containing rubber vulcanizing agent;

9. A food package-comprising a metallic material having at least the surface thereof which is,

to come in contact with the food to be packaged coated with a dried film of hydrogenated resinous polymer of cyclopentadiene. having an average molecular weight of at least 350 in admixture with a sulfur containing rubber vulcanizing agent.

10. Metal foil coated with a dried film of hydrogeriated resinous polymer of cyclopentadiene having an average molecular weight of at least 350 in admixture with sulfur containing rubber vulcanizing agent.

11. A method for producing a metallic foodcontainer element which comprises applyingto sheet metal a coat of a benzene-soluble product resulting from the hydrogenation 'af at least oneflof'a group consisting of resinous polymerized cyclopentadiene, resinous polymerized methyl cyclopentadiene,

ture with a sulfur containing rubber vulcanizing agent, drying said coat, cutting a blank from said sheet metal of a desired shape, and forming said blank to the finished shape of said food container l element.

12. A method for producing a metal cap having sharply formed portions from sheet metal which comprises coating said sheet metal with a benzene-soluble product resulting from the, hydrogenation of at least one of a group consisting of resinous polymerized cyclopentadiene, resinous polymerized methyl cyclopentadiene, and resinous copolymer of cyclopentadiene and methylcyclopentadiene in admixture with a sulfur containing rubber vulcanizing agent, cutting .a blank of desired shape from said sheet metal and die-drawing said blank to the finished shape of said cap.

13. A process for coating a metal surface with an adherent coating which comprises applying to 1 said surface a primer coat of a benzene soluble product resulting from the hydrogenation .of at least one of a group consisting of resinous poly-- merized cyclopentadiene, resinous polymerized methyl cyclopentadiene, and resinous copolymer of cyclopentadiene and methyl cyclopentadienein and resinous copolymer of cyclopentadiene and methyl cyclopentadiene in admix- V admixture with a sulfur containing rubber canizing agent, and applying to said primer ooat after drying a top coat of polymerized vinyl eom- 15. A formed film coated article shapedby dras- Vul- 10m 16% by metal.

tic deformation of sheet metal coated with a composition comprising benzene-soluble hydrogenated resinous polymer of'mon'omeric cyclopentadiene having. a molecular weight ofiat least 450 and from 10% to 16% by weight of said hydrogenated resinous polymer of elemental sulfur, said formed film adhering tenaciously to the formed mm .1. sonar. 

